This would be a long thing coming to be honest. If it were to happen, it would be at the height of an emotional battle. Maybe even the final battle against Salem.
In my headcanon, Jaune starts by healing Cinder. Things are tense but he didn’t want her to die or suffer. Cinder gets confused. She can’t understand why someone who she hurt and took joy in hurting just couldn’t return those painful feelings onto her. Not to mention, his aura power warding off her Grimm arm shows her a power she never considered.
His power of protection. His power to heal and show compassion. It dissipates the Grimm arm that Salem traps and controls her with. It’s a warmth that Cinder’s never known, a power that’s making her feel something that she thought she had lost and she can’t explain it.
She has to return to Salem. In frustration with Jaune challenging her concept of power, she lets him go and that’s where it begins. Those feelings.
They continue to cross paths until the final battle and those feelings continue but Cinder doesn’t know how to say she loves him. She never loved anything more than power for so long so she doesn’t know how to just act on her feelings. Until she protects him too.
In that way, Cinder would be the first to confess to herself and to Jaune that she loves him. When she defends him from a blow from Tyrian. From Salem’s plans in the end.
Whether or not they’d be reciprocated isn’t important as Jaune just holds her. Even he doesn’t know what to say. Sometimes feelings are too intense, too important to just spill out. But he holds her and he makes her feel safe and somehow, at the end of Remnant in the final battle, it’s enough for both of them.
Oh and Pyrrha is full realized in Cinder’s soul and she’s there to guide them along because not even death could separate her and Jaune’s souls. So they’re all in love and healing now.
